Once the applet has been installed, you can add it to a panel as follows:

1. Right-click on the panel on which you want the applet to appear.
2. Select "Add to panel..." in the menu that appears.
3. Find Timer Applet in the list of applets that appears and add it to the panel by double-clicking on it or by dragging and dropping it onto the panel.

Sorry, it didn't work for me. I installed the applet via Synaptic on 10.04. When I go through the "Ubuntu Software Center" route, I see that the applet is installed. However, it doesn't show up in the "Add to panel..." step. The man page is installed, but `which timer-applet` does not produce any results. Does Ubuntu need to be restarted or refreshed in some way?